Summary: TEHRAN (FNA)- The researchers at Washington University in
St. Louis, for the first time, showed that brain plaques in apparently
healthy individuals are associated with increased risk of diagnosis with
Alzheimer's disease years later.

Scientists have long assumed that amyloid brain plaques found in
autopsies of Alzheimer's patients are harmful and cause
Alzheimer's disease. But autopsies of people with no signs of
mental impairment have also revealed brain plaques, challenging this
theory.In two studies published this month in Archives of Neurology,
scientists report that volunteers with brain plaques were more likely to
have declining scores on annual cognitive tests, to show signs of
shrinkage in a key brain area affected by Alzheimer's and to
eventually be diagnosed with the disease."We don't have enough
data yet to definitively say that people who scan positive for these
brain plaques have presymptomatic Alzheimer's disease, but
something is clearly going on that does not bode well for the health of
their aging brains," said John C. Morris, the Harvey A. and
Dorismae Hacker Friedman Distinguished Professor of Neurology and
director of Washington University's Alzheimer's Disease
Research Center (ADRC) and the Friedman Center for Aging.Morris and
others at the ADRC have previously found evidence that Alzheimer's
disease harms the brain for years prior to typical diagnosis. They are
pushing for earlier diagnosis as an essential step to successful
treatment of Alzheimer's disease, but to do that they first have to
seek earlier indicators of disease and then wait years to see if people
with the indicators later develop symptomatic Alzheimer's.According
to Morris, the new papers are early and encouraging indicators that
scientists are on track to pushing back the time at which diagnosis can
be made."We only have a very small number of subjects to date, but
what we're learning so far has been consistent with our
predictions," he said.The new studies were made possible by the
development of an imaging agent, Pittsburgh Compound B (PiB), that lets
scientists use positron emission tomography scans to detect amyloid
plaques in living brains for the first time.Prior to PiB, clinicians
could only verify the presence of brain plaques during autopsies. PiB
scanning of ADRC research participants is directed by Mark Mintun, M.D.,
vice chair for research in radiology and professor of radiology at the
University's Mallinckrodt Institute of Radiology.Martha Storandt,
Ph.D., professor of psychology and of neurology, led one of the studies,
which compared a variety of factors in plaque-positive and
plaque-negative subjects."One of the main things we wanted to know
was whether people who scanned positive for brain plaques scored
abnormally low on cognitive tests," she said."They
didn't, but when we looked at their annual testing records over a
period of years, we saw that the scores of the plaque-positive group
were declining, while those of the plaque-negative group were not,"
she added.Magnetic resonance imaging scans analyzed by Denise Head,
Ph.D., assistant professor of psychology, revealed that brain areas hit
hard by Alzheimer's disease, such as the parahippocampal gyrus,
were smaller in subjects with plaques.In a second study, led by Morris,
researchers tracked a group of 159 volunteers, ages 51 to 88, who were
scanned using PiB between 2004 and 2008. At the time of the scans, none
of the participants showed signs of mental impairment. Twenty-three of
the volunteers later developed mild impairment, and nine members of that
group were diagnosed with Alzheimer's disease.Those who stayed
mentally healthy did not scan positive for plaques, but volunteers later
diagnosed with problems did. Comparisons of the volumes of key brain
structures revealed the same disparities seen in the other study:
subjects who developed mental impairment had significant reductions in
their parahippocampal gyrus and other structures affected by
Alzheimer's.According to Morris, a parallel effort at Washington
University that analyzes cerebrospinal fluid to diagnose
Alzheimer's earlier is also meeting with early success. That
program is led by David Holtzman, M.D., the Andrew and Gretchen Jones
Professor and chair of the Department of Neurology and Anne Fagan,
Ph.D., research associate professor of neurology.Morris speculates that
earlier diagnosis and testing of new treatments may be possible within
the next 10 years."There are risks inherent in Alzheimer's
treatments, so we have to be careful that healthy people who are
selected to receive these treatments to prevent dementia caused by
Alzheimer's disease really do have presymptomatic disease," he
noted.

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